Let's try to clear up the rumor that a Google Phone that reportedly is coming out in January. That is if you can believe any blog that tells you its a rumor.
First of, one has to expect that the phone would not be for the traditional mobile network. Honestly if I was Google I'd build the phone for the only operating 4G network in the USA, Clearwire because from the start Clearwire (ex Xoom) executives has been saying the want a different experience in VoIP and that experience wasn't Skype.
Second Google is an investor in the Clearwire venture, which makes me think the phone won't be made by HTC, but instead will be built by partner, Motorola. But Google has more than money to put into Clearwire, something that was made clear after Google didn't put hard cash into the recent Clearwire fund raising.
The reason I think that Google would be playing first with Clearwire over the usual 3G networks has to do more with not competing with the iPhone or it's own "Android" phones with the carriers. While the Google Phone would likely carry lots of Android like qualities, when you link up Android and Chrome as Sergey Brin alluded to, you can see another reason why the Clearwire 4G network makes more sense.
One other piece of the puzzle is the combined capabilities of GoogleTalk/GoogleVoice/Gizmo5 capabilities. As you keep looking at the pieces Google has been assembling, they all have open at their core, using XMPP and SIP based protocols.
One last thing, just as Apple was all about the software/hardware experience with the iPhone due to their approach called "Radical Integration" Google's experience is all about the Network and the cloud. To operate effectively, the "cloud" needs a speedy network, one that is not bogged down by legacy voice traffic and legacy voice thinking. Of the four USA networks, the only carrier that thinks network first, in Sprint, and Sprint, like Motorola, Comcast and Google, is also a backer of Clearwire.
To me the picture of the Google Phone is really Clear.